Apparatus and method for repairing failure spots on subterranean well tubulars using shock waves

ABSTRACT

An apparatus and method are disclosed for the repair of failure spots, such as holes, crevices, and the like, along a first tubular section, such as casing section(s) in subterranean wells. The apparatus includes a housing made of a malleable material, such as steel, which is responsive to shock waves generated by an explosive material, such as a detonator cord, carried inside the housing. The explosive detonator cord is activated to generate shock waves within the housing to expand the malleable housing to conform to the wall holes, openings and failure spots in the casing. Thereafter, a head, selectively securable to the housing, is disengaged from the housing during retrieval of the head after activation of the detonator cord, to retrieve the head from the well and leave the malleable housing intact and across the failure spots.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus and method for the repair offailure spots along a first tubular conduit, such as casing, in asubterranean well.

2. Brief Description of the Prior Art

Subterranean wells, such as oil, gas or water wells, oftentimes arecompleted with the introduction and cementing in place a long string oftubular sections of metallic casing. Since the expected production lifeof such a well has been known to last decades, and in view of the factthat the abrasive well fluids and treatment chemicals flowinginteriorally of the casing often result in defects, such as small holes,pock marks leading to small holes and cracks, (“failure spots”) it isnot at all surprising that a failure in circulation of the fluidsoftentimes results, with the holes eventually getting larger and largerand even penetrating through the cement securing the casing within thewell. It is therefore necessary from time to time to inspect the casingfor such defects and attempt to repair them, as opposed to retrievingthe entire casing string and running and setting another string ofcasing, or running a smaller diameter casing string which greatlyreduces the diameter available for production.

U.S. Pat. No. 6,536,349, entitled “Explosive System For Casing DamageRepair”, to Patterson, et. al., discloses use of a liquid explosive torepair a damaged portion of casing where the damaged portion restrictsaccess through the casing string. However, this concept does not addressthe problem of actual repair of failure spots, such that the originalcasing section is returned to normal or substantially normalspecifications for subsequent production or other actions.

SUMMARY OF THE INVENTION

The invention related to an apparatus and method for the repair offailure spots in and along a first tubular conduit, such as casing,placed within a subterranean well. The apparatus includes a malleablecylindrical housing mean which is responsive to shock waves generatedwithin the interior of the housing to outwardly and radially expand thehousing across the and into the failure spots. Means, such as adetonator cord, are provided within the housing to generate the shockwaves upon explosive activation for expansion of the housing means.Actuation means, such as an electric activator, are also provided foractivating the detonator cord, or the like. In one embodiment, a headelement is provided which has means for securing the head element to oneend of the housing. The head element is selectively disengageable fromthe housing after activation of the detonator cord or charge, such thehousing remains in place over the repaired failure spots and the head isretrieved by wire line or conduit, out of the well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a section of first tubularconduit, or casing, cemented within a subterranean well, and containingfailure spots that are required to be repaired.

FIG. 2 is a view similar to that of FIG. 1, illustrating the positioningof the apparatus of the present invention on a wire line or otherconduit and positioned to straddle the failure sport on the casingconduit.

FIG. 3, is an illustration similar to that of FIG. 2, illustrating theapparatus during activation and explosion of the detonator cord togenerate shock waves to expand the housing into and over the failuresport in the casing.

FIG. 4, illustrates the housing covering the failure spots, with thehead element shearingly disengaged from the housing and retrieved fromwithin the well.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring to FIG. 1, there is shown a subterranean well W. The wellW includes previously run and set a first conduit string or casing C-1.As shown, the casing C-1 has a series of small holes or defects Hlocated longitudinally and radially around a section of the casing C-1.These “failure spots” are required to be repaired.

As shown in FIG. 2, the apparatus 100 is shown positioned within thewell W and straddeling the failure spots H. The tool 100 is run into thewell on an electric line, tubing, or wire cable, or the like,illustrated as 102. The tool 100 is comprised of two major parts: anupper head element 103, to which is secured the cable 102; and acylindrical housing 105, made of a malleable material, such as iron,thin sheet metal alloys, tin or the like. The housing 105 may be made ofany similar malleable material which will permit radial expansion inresponse to shock waves generated by an explosive charge within thehousing 105. The head element is secured to the uppermost portion of thehousing 105 by means of shear pins 104. The pins 104 will separate whena predetermined amount of shear or pulling gforce is applied through thepins 104 as the head element 103 is retrieved from the well W subsequentto the repair of the failure spots, as hereinafter described.

An electric line 101 is carried through the head element 103 and intothe housing 105 for securement to a detonator cord or charge 106. Asused herein a detonator or detonating cord is a round, flexible cordcontaining a center core of high explosive. It is relatively insensitiveand requires a proper detonator, such as a No. 6 strength cap, forinitiation. Detonating is used to initiate other explosives, its abilityto detonate the other depends in part on the density of the highexplosive core (usually pentaerythritol tetranitrate: PETN) or thegrains of PETN per linear foot of cord. The most widely used cords haveapproximately 25 to 60 grains-per foot (5.3 to 12.87) grams per meter),although core load with as little as four grains per foot and up to 400grains per foot is available.

As further used herein, the term “detonating cord” or “detonator” hasits usual meaning of flexible, coilable cord having a core of highexplosive, the core being a secondary explosive, usually PETN. The term“low energy detonating cord” or “LEDC”, is conventionally used to meandetonating cord which will not reliably initiate itself when placed incontact with itself by coiling or crossing lengths of the cord, andwhich will not, when in an ungathered configuration, reliably directlyinitiate a less sensitive or secondary explosive receptor charge, e.g.,those that comprise secondary explosive materials (e.g., Pentolitemixtures of PETN and trinitrotoluene (“TNT”) to the substantialexclusion of primary explosive materials. Such ungathered configurationsinclude, e.g., simple surface-to-surface contact between an uncoiledLEDC and a receptor charge and the insertion of the end of asubstantially straight length of LEDC into a bore in the body of areceptor charge. For This reason, LEDC is typically used to initiate amore sensitive, high energy amplifying device such as a detonator whichis sensitive to the LEDC (usually by virtue of containing a primaryexplosive material) and which generates an output signal sufficient toinitiate the less sensitive secondary explosive receptor charge.

Now referring to FIG. 3, after the tool 100 is located within the well Wto straddle the failure spots H in the casing C-1, the detonator cord106 is exploded by sending an electric signal through electric line 101from the top of the well W or other location within the well W. As thedetonator cord 106 is activated, an explosion occurs to direct shockwaves radially outwardly and against the housing 105. Because of themalleable nature of the construction of the housing 105, the shock wavesS will cause it to expand outwardly, filling and otherwise repairing thefailure spots H. Thereafter, the head element 103 is released from thehousing 105 as the line or tubing 102 is pulled upwardly, such the shearpins 104 shear. The housing 105 is thus left in the well W.

Although the invention has been described in terms of specifiedembodiments which are set forth in detail, it should be understood thatthis is by illustration only that the invention is not necessarilylimited thereto, since alternative embodiments and operating techniqueswill become apparent to those skilled in the art in view of thedisclosure. Accordingly, modifications are contemplated which can bemade without departing from the spirit of the described invention.

1) An apparatus for introduction into a subterranean well on a conduitfor the repair of failure spots along a first tubular section encasedwithin said well, comprising: (a) a malleable cylindrical housing meansresponsive to shock waves generated within said housing to outwardly andradially expand said housing across and into said failure spots; (b)means within said housing to generate shock waves to initiate expansionof said housing; and (c) actuation means for actuating said means togenerate said shock waves. 2) The apparatus of claim 1, furthercomprising: a head element initially secured to one end of said housingand selectively disengagable there from subsequent to expansion of saidhousing, said head element having means for securing said conduitthereto for introduction, setting and retrieval of said head elementwithin the well, whereby the expanded housing is retained within saidwell and the head is retrieved from within the well. 3) The apparatus ofclaim 1 wherein the means within said housing to generate shock wavescomprises an elongated section of detonator cord. 4) A method for therepair of failure spots within or along a first tubular section encasedwithin said well, comprising the steps of: (1) introducing into the wellon a conduit an apparatus, comprising: (a) a malleable cylindricalhousing means responsive to shock waves generated within said housing tooutwardly and radially expand said housing across and into said failurespots; (b) means within said housing to generate shock waves to initiateexpansion of said housing; and (c) actuation means for actuating saidmeans to generate said shock waves; (2) positioning the apparatus in thewell whereby the cylindrical housing means straddles the failure spots;and (2) actuating the actuation means to cause said means within saidhousing to generate shock waves to initiate expansion of said housing,whereby said housing is expanded into and across said failure spots. 5)The method of claim 4 wherein said apparatus further comprises a headelement initially secured to one end of said housing and is selectivelydisengageable there from, and means for securement of said head elementfor introduction, setting and retrieval of said head element within thewell; and further comprising the step of releasing the head element fromthe housing subsequent to generation of said shock waves and retrievingthe head means from within the well.